The present invention relates to an image processing apparatus, an image processing method and a recording media on which software for executing the image processing is recorded. More specifically, the present invention pertains to an image processing apparatus, an image processing method and a recording media on which software for executing the image processing is recorded that are capable of creating a frequency-processed image such as a soft-focused image, a sharpness-enhanced image, and the like, when the image processing apparatus is used in a color image reproducing system, which reproduces a color image as a visible image in the following manner. That is, a subject or an image is photoelectrically read, and original image signals, which are obtained by converting the image into digital signals and represent an amount proportional to an optical density or to a logarithmic exposure amount are subjected to image processing.
There have been proposed color image reproducing systems. With the color image reproducing systems, a color image recorded on a negative film, a reversal film, a color print, and the like is photoelectrically read with a photoelectric conversion device such a charge coupled device (CCD) or the like; the color image is converted into digital signals and stored in an image signal storing unit such as a frame memory or the like as original image signals; the color image stored in the image signal storing unit is subjected to image processing; subsequently, the thus processed image signal is reproduced on a recording material such as a color paper or the like, or on a cathode ray tube (CRT).
According to the color image reproducing system, even if a color image is recorded under improper recording conditions such as underexposure, overexposure, and the like and recorded on a negative film, a reversal film, a color print, or the like, the color image reproducing system can reproduce resulting original image signals as a color image having desired colors and gradation by subjecting the original image signals to image processing. In addition, the color image reproducing system can reproduce a color image recorded on a negative film, a reversal film, a color print, and the like as a color image having different colors and gradation, when desired.
In contrast, although a soft-focused image is created by multiple exposure when a photograph is taken or when a photograph is printed, the multiple exposure is a time-consuming technology. Thus, there has been strongly desired to create a soft-focused image, which has the same effect as that created by the multiple exposure, by means of the above color image reproducing system based on a color image recorded on a negative film, a reversal film, a color print, and the like without the execution of the multiple exposure.
To satisfy the desire, the applicant has disclosed an image processing apparatus which can create a soft-focused image by carrying out digital image processing in the above digital color image reproducing system in Japanese Unexamined Patent Publication No. 9-172600. The image processing apparatus, which is disclosed in the publication, is arranged such that a color image is read and subjected to logarithmic (LOG) conversion in the above color image reproducing system; thereafter, original image signals are obtained by subjecting image signals stored in a frame memory to color conversion; subsequently, the original image signals are subjected to unsharp mask processing to thereby obtain unsharp image signals; then, image signals for creating a soft-focused image is created by combining the unsharp image signals with the original image signals at a prescribed rate.
Incidentally, when a photographic image is handled as digital data, it is an ordinary practice that image signals, which have been input or read, that is, image data showing an amount corresponding to or in proportional to subject luminance or intensity of light incident to the subject such as data corresponding to subject illuminance or exposure amount (hereinafter called as exposure amount data) are processed so that they are converted into data representing an amount, which is relatively linear to human eyes and is proportional to an optical density or to a logarithmic exposure amount (hereinafter, referred to as xe2x80x9cdensity dataxe2x80x9d); then, various kinds of image processing steps are carried out to the converted data.
In the image processing apparatus disclosed in Japanese Unexamined Patent Publication No. 9-172600, original image signals (exposure amount data), which have been obtained by reading a color image, are subjected to logarithmic (LOG) conversion and converted into density data; thereafter, unsharp image signals are created; and the unsharp image signals are added to the original image signals at an arbitrary rate. As a result, the image processing apparatus can also create an image having an soft-focusing effect.
It is true that when soft focus processing is carried out using the image signal data converted into the density data as carried out by the above technology, a processed image is finished to have soft feeling. However, the technology has a problem that it cannot produce the loss of definition of light from a bright portion to a dark portion, that is, so-called flare feeling, which can be produced when an image is recorded with an actual camera in a soft-focus mode.
Further, with the technology, the adding rates of the original image and the unsharp image, which are added to each other as density data, are unchanged at any portion of one image. Accordingly, there is also a problem that when the adding rate of the unsharp image is increased to provide an image with soft feeling, the core of the image is made excessively unsharp and the edge of the image, to which human eyes are most sensitive, tends to be felt only unsharp. Whereas, there is an additional problem that when a soft effect is restricted and the adding rate of the original image is increased to emphasize the core of the image, the badness of graininess is made noticeable.
On the other hand, there is a further problem that when sharpness emphasizing processing is carried out using the density data at the time a color image is reproduced on a finished print from a color negative film and a color reversal film, a processed image is made sharp, but the graininess of a human skin is made bad.
An object of the present invention is to solve the problems of prior art and to provide an image processing apparatus, an image processing method and a recording media on which software for executing the image processing is recorded that are capable of obtaining a soft-focused image having an effect near to flare, which is obtained in the soft-focusing executed in an analog mode when an image is actually recorded with a camera and capable of obtaining a processed image having an optimum frequency processing effect such as a sharpness-enhanced image, in which the sharpness of the image is enhanced while restricting the deterioration of the graininess of a human skin. The image processing apparatus and method are arranged such that when frequency-processed images such as the soft-focused image, the sharpness-enhanced image, and so forth, are to be created by subjecting digital original image signals, which have been obtained, to image processing, frequency processing such as soft-focus processing, sharpness enhancement processing and the like is carried out by changing the digital data of the original image signals, which is represented by a logarithmic scale, a power scale or the like, to image signal data which represents an amount corresponding to or proportional to the amount of the luminance of the subject or of the intensity of incident light, or corresponding to reproduced luminance, for example, the luminance of the subject or the intensity of the incident light before they are subjected to logarithm (LOG) conversion or power conversion, or the reproduced luminance processed to raise an inclination of its gradation by taking an influence of the flare or an improvement of a freshness or briliance in color or the like into consideration.
To achieve the above object, the inventors have diligently studied to create a soft-focused image having flare feeling which can be realized in the analog mode when an image is recorded by a camera. As a result, the inventors have achieved the present invention by finding that when soft focus processing is to be applied to digital image signal data, it is preferable to carry out image processing by changing data (for example, density data), which represents an amount proportional to an optical density or a logarithmic exposure amount, to exposure amount data. The reason is that when the analog mode, in which an actual soft-focused image is created by recording an image with a camera using a soft-focus lens or by recording an image or printing a picture by multiple exposure, is taken into consideration, it is conceived that image processing is applied to an image signal (for example, exposure amount data) which represents an amount proportional to the luminance of a subject having been input or to the intensity of incident light.
More specifically, the present invention provides an image processing apparatus for creating digital soft-focusing image signals, which create an soft-focused image, by subjecting digital original image signals to image processing. The image processing apparatus comprises a means for converting the original image signals into conversion image signals which represent an amount corresponding to the luminance of a subject, the intensity of incident light, or reproducing luminance; a means for creating soft-focus processing conversion image signals by subjecting the conversion image signals to prescribed smoothing processing; and a means for inversely converting the soft-focus processing conversion image signals into the digital soft-focusing image signals.
The present invention provides the image processing apparatus, wherein the means for creating the soft-focus processing conversion image signals comprises a means for creating unsharp image signals from the conversion image signals and an addition mean for adding the conversion image signals to the unsharp image signals at a prescribed adding rate to thereby create the soft-focus processing conversion image signals. More specifically, it is preferable that the smoothing processing creates. the unsharp image signals from the conversion original image signals and adds the conversion original image signals to the unsharp image signals at the prescribed adding rate.
It is preferable that the means for creating the soft-focus processing conversion image signals further comprises a gain adjustment means for adjusting at least one of the gains of the medium frequency component and the high frequency component of the conversion image signals, wherein the adding means adds the conversion image signals, whose gain has been adjusted by the gain adjustment means, to the unsharp image signals to thereby create the soft-focus processing conversion image signals.
Further, it is preferable that the means for creating the soft-focus processing conversion image signals further comprises an adding rate adjustment means for adjusting the adding rate at which the gain-adjusted conversion image signals are added to the unsharp image signals.
It is preferable that the means for creating the soft-focus processing conversion image signals further comprises an adding rate adjustment means for adjusting the adding rate at which the conversion image signals are added to the unsharp image signals.
Further, it is preferable that the means for creating the soft-focus processing conversion image signals further comprises a determination means for determining the density in an image using the original image signals, wherein the adding rate adjustment means adjusts the adding rate in accordance with the density in the image determined by the determination means.
It is preferable that the means for creating the unsharp image signals is an unsharp mask processing means including a lowpass filter.
It is preferable that the means for creating the unsharp image signals comprises a means for converting the conversion image signals into a luminance signal and an unsharp mask processing means for subjecting the luminance image signals, which have been converted into the luminance signal, to unsharp mask processing.
It is preferable that the original image signals and the digital soft-focusing image signals are image signals which represent an amount propotional to an optical density or a logarithmic exposure amount.
The present invention provides an image processing apparatus for creating digital frequency processing image signals, which create a frequency-processed image, by subjecting digital original image signals to frequency processing. The image processing apparatus comprises a means for converting the original image signals into conversion image signals which represent an amount corresponding to the luminance of a subject, the intensity of incident light, or reproducing luminance; a frequency processing means for carrying out frequency processing using the conversion image signals; and a means for inversely converting the conversion image signals, which have been subjected to the frequency processing, into the digital frequency processing image signals.
In the above arrangement, it is preferable that the frequency processing is soft-focus processing or sharpness enhancement processing, and the frequency processing means is a soft-focus processing means or a sharpness enhancement processing means.
Moreover, the present invention provides an image processing method, comprising the steps of: converting digital original image signals into conversion image signals which represent an amount corresponding to subject luminance, incident light intensity, or reproducing luminance;
creating soft-focus processing conversion image signals by subjecting the resultant conversion image signals to preset smoothing processing; and
inversely converting the resultant soft-focus processing conversion image signals into digital soft-focusing image signals.
Preferably, the soft-focus processing conversion image signals are created by creating unsharp image signals from the conversion image signals and adding the conversion image signals to the unsharp image signals at preset adding rate.
Preferably, the soft-focus processing conversion image signals are created by adjusting at least one of the gains of the medium frequency component and the high frequency component of the conversion image signals and adding the gain-adjusted conversion image signals to the unsharp image signals.
Preferably, the preset adding rate, at which the gain-adjusted conversion image signals are added to the unsharp image signals, is adjusted.
Preferably, the preset adding rate, at which the conversion image signals are added to the unsharp image signals, is adjusted.
Preferably, the density in an image is determined using the original image signals, and the preset adding rate is adjusted in accordance with the determined density in the image.
Preferably, the unsharp image signals are created by unsharp mask processing executed using a lowpass filter.
Preferably, the unsharp image signals are created by converting the conversion image signals into a luminance signal and subjecting luminance image signals, which have been converted into the luminance signal, to unsharp mask processing.
Preferably, the original image signals and the digital soft-focusing image signals are image signals which represent an amount proportional to an optical density or a logarithmic exposure amount.
Moreover, the present invention provides an image processing method, comprising the steps of: converting digital original image signals into conversion image signals which represent an amount corresponding to subject luminance, incident light intensity, or reproducing luminance;
carrying out frequency processing using the resultant conversion image signals; and
inversely converting the resultant frequency-processed conversion image signals into digital frequency-processed image signals.
Preferably, the frequency processing is soft-focus processing or sharpness enhancement processing.
Moreover, the present invention provides a recording medium on which software for executing the image processing methods according to the above-described aspects of the present invention is recorded.
The image signals to be subjected to the soft-focus processing of the present invention may be the image data which has been captured by a camera when it records a subject (scene), that is, they may be the image data which has been obtained by an input device such as a scanner and the like when it reads an image recorded by an ordinary camera on a photographic film. Further, they may be the image data which has been recorded by a directly-recording camera type input device such as a digital camera, a digital video camera, and so forth and has been directly obtained thereby. Furthermore, they may be the image signals which have been subjected to picture-creation processing that is ordinarily carried out when image data captured by the various types of the cameras (input devices) is finished to a print, that is, they may be the image signals which have been subjected to gradation processing and the like which are carried out in consideration of the effect of flare when a subject is observed as well as the improvement of color vividness, and so forth.
In the present invention, the image signals, which have been output from an input device after they are subjected to logarithmic conversion or to power conversion or after they are converted into the digital luminance output value of target gradation, are referred to as image signals which represent a value proportional to an optical density or to a logarithmic exposure amount. The data representing the image signals is referred to as density data. Therefore, the digital original image signals which are input to the image processing apparatus of the present invention, the digital soft-focusing image signals which are obtained in the apparatus, and the digital output image signals which are output from the apparatus are image signals that represent the amount proportional to the optical density or to the logarithmic exposure amount.
In contrast, the image signals, which are directly detected by the input device before they are subjected to the logarithmic conversion or to the power conversion or before they are converted into the digital luminance output value of the target gradation, for example, the image signals, which correspond to subject illumination intensity, subject reflectance, and an exposure amount, are referred to as image signals, which represent an amount corresponding to or proportional to the subject luminance or the incident light intensity. The data representing the image signals are referred to as exposure amount data. In addition, the image signals, which are obtained by subjecting the image density data supplied from the input device to the above picture creation processing and then converting the resultant processed data to signals before they are subjected to the logarithmic conversion or to the power conversion or before they are converted into the digital luminance output value of the target gradation are referred to as image signals which represent an amount corresponding to or proportional to reproduction luminance. The image signals are processed similarly to the image signals which represent the amount corresponding to or proportional to the subject luminance or the incident light intensity. Thus, the data representing the image signals is referred to as the exposure amount data.